A lawyer for Viktor and Amalija Knavs said that the first lady's Slovenian mom and dad took the citizenship oath on Thursday in Manhattan.
"It's a dirty - a dirtier word", he said, adding that "it stands for a bedrock of our immigration process when it comes to family reunification".
The Republican president argues that the system steals jobs from Americans and threatens national security, calling for a merit-based system that preferences more educated, English-speaking professionals.
"Under the current broken system, a single immigrant can bring in virtually unlimited numbers of distant relatives", Trump told the nation, adding that part of his fourth pillar, "chain immigration" practices were coming to an end. It's unclear when the Knavses obtained permanent residency in the USA, the Times reports, but Wildes said they met the five year requirement.
They came and went from the ceremony at a federal building flanked by Homeland Security police. The time to process an application for naturalization in New York City typically ranges from 11 to 21 months, according to the U.S. Citizenship and Immigration Services.
Melania Trump became a citizen in 2006 after obtaining a green card.
Typically, naturalisation ceremonies at 26 Federal Plaza are large events, where groups of immigrants are sworn in as citizens en masse, after reciting an oath and the Pledge of Allegiance.
Asked by the New York Times if they had obtained citizenship under a program derisively branded "chain migration" by the president, Wildes replied: "I suppose".
Kaitlyn Schallhorn is a Reporter for Fox News.
The couple met in Sevnica, Slovenia in 1966, and Melania was born in the same town. Viktor, 74, was a auto dealer while Amalija, 73, worked in a textile factory.
The US allows a number of ways for US citizens and legal permanent residents to sponsor family members to come to the US permanently, including categories for parents, adult siblings and adult children, married and unmarried. Melania was not present for the ceremony as she was in Bedminster, New Jersey, at the Trump National Golf Club, where the President is now staying.
US President Donald Trump's parents-in-law have become US citizens in a private ceremony. "We saw an example of that today".